我正在使用HiveMQ Java客户端连接到HiveMQ代理。阻止客户端订阅服务器未使用任何消息。使用 MQTTBox 发布和订阅工作正常。这是代码.我正在关注HiveMQ Java客户端文档
public class MQTTMain {
public static void main(String[] args) {
Mqtt3BlockingClient pubClient = MqttClient.builder()
.useMqttVersion3()
.identifier("pub")
.serverHost("hostaddress")
.serverPort(1883)
.buildBlocking();
Mqtt3BlockingClient subClient = MqttClient.builder()
.useMqttVersion3()
.identifier("sub")
.serverHost("hostaddress")
.serverPort(1883)
.buildBlocking();
pubClient.connectWith().keepAlive(10000).send();
publish(pubClient, "test/topic", "test");
subClient.connectWith().keepAlive(10000).send();
subscribe(subClient, "test/topic");
while (true) {
}
}
public static void subscribe(Mqtt3BlockingClient client, String topic) {
try (final Mqtt3Publishes publishes =
client.publishes(MqttGlobalPublishFilter.ALL)) {
try {
publishes.receive(1, TimeUnit.SECONDS)
.ifPresent(System.out::println);
publishes.receive(10000, TimeUnit.MILLISECONDS)
.ifPresent(System.out::println);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
} catch (Exception e) {
// TODO: handle exception
}
client
.subscribeWith()
.topicFilter(topic)
.qos(MqttQos.AT_LEAST_ONCE)
.send();
}
public static void publish(Mqtt3BlockingClient client, String topic,
String payload) {
client
`enter code here`.publishWith()
.topic(topic)
.qos(MqttQos.AT_LEAST_ONCE)
.payload(payload.getBytes())
.send();
}
}
Maven 依赖:
<!-- MQTT Client -->
<dependency>
<groupId>com.hivemq</groupId>
<artifactId>hivemq-mqtt-client</artifactId>
<version>1.0.0</version>
</dependency>
我错过了什么吗?任何指针都会很有帮助。
您必须先订阅,然后才能接收消息。
Publishes.receive 是一个阻止操作,因此它会等到收到消息。您将在接收操作后订阅。你应该做这样的事情:
Mqtt3BlockingClient client = Mqtt3Client.builder()
.identifier("sub")
.serverHost("hostaddress")
.serverPort(1883)
.buildBlocking();
client.connect();
try (final Mqtt3BlockingClient.Mqtt3Publishes publishes =
client.publishes(MqttGlobalPublishFilter.ALL)) {
client.subscribeWith().topicFilter("test/topic").qos(MqttQos.AT_LEAST_ONCE).send();
publishes.receive(1, TimeUnit.SECONDS).ifPresent(System.out::println);
}